Removing cured paint coatings from large volumes of racks, hangers or other paint line equipment has been a problem for production finishers. Heavy buildups of paint can flake off onto the work piece and prevent a fixture from working properly, and even light buildup can interfere with the quality of an electrostatic painting process.
Several techniques have been developed in attempts to satisfactorily remove paint coatings on such equipment. One such technique is to debond or dissolve the organic coating in an chemical solvent bath. Such solvents include methylene chloride and trichloroethane. While these solvents are often effective for debonding the paint coating from the substrate, they generate chemical waste such as stripping sludges, which result in disposal and pollution problems. Additionally, long soaking times are often required, which makes this method undesirable for continuous on-line operations.
Another technique involves applying a liquefied inert gas to the support and/or to the built-up paint layers to cause embrittlement of the paint and lessen the bond between the support and the built-up paint layers. The paint layers while still under cryogenic conditions are removed from the support by impact or blasting. The impact can be by abrasive particles which are blasted at the surface by air or mechanical means, or may be a simple mechanical impact. Repeated use of such abrasive particles or impacts tends to wear down or deform the hangers, especially where the hangers contain screws, springs or similar objects. See for example U.S. Pat. Nos. 4,554,025 and 4,705,574.
In a further technique for removing unwanted paint layers from racks, hangers, etc., a coating is formed on the hangers prior to their use in painting operations. The coating has minute bubbles on the surface. After accumulation of paint over the coating a mechanical impact to the hanger forms a gaseous layer between the hanger and the paint layers. Thereafter, the paint layers are peeled from the hanger by mechanical means. See for example U.S. Pat. No. 4,867,900.
In U.S. Pat. Nos. 5,017,303 and 4,844,833 a paint peeling composition and method for removing uncured paint from an object is disclosed. The method involves coating an object, such as floor grates in a paint spray booth, with a water soluble polyvinyl alcohol, polyvinyl acetate, or acrylic resin layer which incorporates thermally expandable microballoons. Unnecessary paint is removed from the objects by immersion in hot water. The hot water expands the thermally expandable microballoons and dissolves or disperses the carrier layer thereby removing the paint.